Purpose: To explore the CT findings and pneumonia progression pattern of Covid 19 in unvaccinated patients, and to compare findings in vaccinated patients with Covid 19.

Method: In this retrospective comparative study, a total of 15874 patients with COVID-19 were included: 1281 patients with wild type (748 men), 7945 with Alpha variant (4972 men), 4233 with Delta variant (2548 men) and 2415 with Omicron and subtypes (1301 man). There were 7646 patients after vaccine were induced. In our country we had Sinopharm, Astra Zeneca, Sputnik V, Pfizer and Moderna vaccines. CT examination was performed in all patients.

Results: 1028 patient received at least one dose of vaccine, 6618 unvaccinated, and 8228 unvaccinated before vaccine was included. In vaccinated group 3 patient finished lethal, in unvaccinated group there were 125 deaths, and in unvaccinated before vaccine the were 251 lethal cases. Lethal patients (in vaccinated) were 64, 65 and 76 years old, immunocompromised. All three of them were without symptoms almost until death (64 and 65 years old had first, but severe symptoms only few hours before death, 76 years old had first symptoms three days before death). In vaccinated group ground glass opacity (GGO), crazy paving, subpleural fibrosis with consolidation and repairing changes were found in significantly lower percent then in other groups. Severity score was lower, almost all patients with severity score 0-5 (11 patients were with severity score 10-18). Illness was finished in less days

Conclusions: Prevention is the best way to deal with covid 19. Patients with three or more doses had less problems, mostly fatigue. Long covid in vaccinated patients was present but in mild forms.